Foam or other type chemicals are frequently added to the water used in fighting fires. A desired ratio of chemicals to total flow is desirable but this is difficult to achieve and maintain since the total flow is liable to change quite often, for instance, due to change in the supply pressure or due to the adding or subtracting of hoses from the water supply.
Conventional chemical injection apparatus generally uses manually operated mechanical mixing apparatus.
The present invention provides means to automatically meter a certain ratio of chemicals into the water supply and this ratio is maintained electrically.
In one embodiment, a servo motor responsive to the total flow controls the pump for the chemical
In another embodiment a valve is automatically controlled to control the chemical.